A crofter has to get to his herd of sheep quickly as he has been told they are being attacked by a dog. His sheep are on the other side of a steep hill. He can run over the hill (3 miles) at 4 miles an hour or take his tractor via an old dirt track which is 5 miles at an average of 6 miles an hour or he can drive his car along a very narrow winding road but this is 14 miles and he can only go at 18 miles an hour on average.